In an injection molding assembly process for fabricating packaged plastic electronic devices, IC devices are encapsulated with a molding compound (e.g., an epoxy resin) in order to provide protection for the packaged device from the external environment. This encapsulation process is also called a molding process.
The encapsulation process generally involves placing IC devices, typically positioned on a sites on a substrate strip such as die pads of a leadframe strip, in one or more cavities of a mold. Liquid molding compound is then forced through chambers of a mold, forming culls, which subsequently flows through a series of mold runners and subrunners. From the subrunners, the mold compound flows through a series of gates and enters the mold cavities, thus forming encapsulant bodies on the IC devices. Excess encapsulant, a byproduct of the encapsulation process, generally referred to as cull runners, are ejected from the runners and subrunners while still connected to the gates of the encapsulant bodies. The cull runners can be removed by a process called degating with the aid of an apparatus called a “degater” or “degater assembly” that includes degate punchers.
The purpose of degating is to remove the cull runners from the encapsulant bodies that protect the IC device. In the case the substrate comprises a lead frame strip, degating may comprise using a first and a second degate puncher using pressure provide by a hydraulic system. The degate punchers both pass through spaced apart circular holes in side rails of the lead frame strip to push through the cull runner to sever (detach) the cull runner from the encapsulated IC device. Tilting then allows the cull runners to be deposited in a cull bin. However, because the mold tends to adhere to all surfaces of the lead frame strip, the removal of the cull runner during punch degating can twist the lead frame strip that can be flexible enough to cause damage such bow or warp to the surrounding lead frame surface thereof.